Method of coating articles



Patented Jan. 11, '1927.

UNITED STATESPAT ENT OFFICE.

ALBERT FERDINAND LINDSTROM, OF N UTLEY, NEW JERSEY, ASSIGNOR TO WESTING-HOUSE LAMP COMPANY, A COEPORATION OF PENNSYLVANIA.

METHOD OF COATING ARTICLES.

No Drawing. Application filed July 7,

This invention relates to the method of applying a coating to a smoothsurface and especially to a vitreous materlal and more particularlyrelates to the method of affixing a coating to anincandescent-electric-lampbulb. I

One of the objects of the invention is to provide a method ofexpeditiously and efliciently applying a coating to a bulb.

Another object is to apply a coat-mg comprising a plurality of layers.

A further object is to prepare a bulb for treatment so that a coatingapplied thereto will immediately set.

Other objects andv advantages will be ap: parent from the followingdescnption.

Although the present method may have general application, it ispartlcularly adapted for use in connection with the process of coatinglamps in which a coating is sprayed upon the lamp by a compressedflllld', such as air.

In the use of incandescent lamps, especially those of high intensity, itis very often desirable, under various conditions, to diffuse theemanating light rays. Var1ous expedients have been employed foraccomplishing this result, as, for instance, by the disposition of atranslucent screen between the light source and the user, or themtensity of the light may be directly con-. trolled by frosting oretchlng the bulb or by applying thereto a superficial coating of apreparation such as an enamel or the l1k e. Certain difliculties havebeen encountered in the production of a suitable preparation that wouldadhere to the bulb of a lamp and be resistant toheat and to the solventaction of water.

An example of a coating which, however, meets the requirements essentialto the efficient coating of a bulb maybe found 1n copending applicationto Aaron M. Hageman and Albert F. Lindstrom, Serial No. 608,7 7 2 filedDecember 23, 1922 and assigned to Westinghouse Lamp Company and thepresent method aims to improve the method of applying the coating as setforth in this application and in connection with other coatin s.

The above mentioned application consists of a compound which includessuch coloring pigments and other materials as may pro- 1922. Serial No.573,440.

vide a translucent surface which may applied to a lamp bulb. As setforth in that application, the enamel may be prepared by mixing suitableamounts of powdered ka 01in with a solution of sodium silicate and thenplacing this mixture in a ball-milling mixer and operating the mixer fora given period to produce a fluid of a suitable consistency. Variousmodifications of this mix ture may be made to meet coloring andlight-diffusing requirements of a lamp.

Themixture is preferably applied to a bulb by means of'a spray gun inwhich air under pressure is employed to drive or spray the fluid uponthe surface to be coated or enameled, after which the coated surface issubjected to a heat'treatment for a given period for the purpose ofaflixing the coating to the surface. The coating is next subjected tothe application of a suitable heated setting solution of a neutral saltsuch as ammonium chloride which will effoot the necessary chemicalreaction to render the coating insoluble in water. The setting solutionmay, however, be applied cold if desirable, in which case the bulbs maybe passed through a heat zone. The bulbs are through an oven.

Although the above process provides for the efficient and uniformcoating of bulbs, it has been found desirable to provide for the morerapid application of the coating, that is, to coat a given number ofbulbs in a rela tively small amount of time and this is accomplished inthe present invention by preheating the bulbs and applying the coatin tothe heated surfaces. It has been foun that a coating, as, for example,the one briefly outlined above will set more quickly when applied to awarm surface and in practice such a coating hardens or setsinstantaneously upon striking the heated surface. Furthermore, a coatingmaterial which is sprayed upon the bulb strikes it in a series ofsuccessive deposits, each deposit forming a very thin layer and, since,as stated, the particles set immediately, the continued ap plication ofthe material by meansof the spray causes a coating of any desiredthickness or density to be built up. The building up of the coating maybe construed to mean the depositing of a plurality of layers which thenwashed and finally dried by passage are applied in rapid succession andeach layer, although a separate entity when ap plied, ultimatelycontributes to the produc tion of a coating of a thickness dependingupon the temperature to which the bulb is heated andto the manipulationof the spray un. By this method, a very desirable coating is produced,inasmuch as it is well known that a more satisfactory sheen or luster 18produced in coatings which are formed by the application of severallayers, one upon the other, but, heretofore, the t me consumed by thisoperation was prohibitive by reasoii of the time consumed. Bypre-heating the surface tobe coated, a bulb may be sprayed and a coatingof a plurality of layers ro'duced in a time interval of approximatelyone-half that which was heretofore necessary to apply to the usualsingle layer of material of the same thickness.

It is obvious, that coatings of various degrees of translucency maybeapplied to lamps to meet ditl'erent lighting conditions and wherecolored coatings are desirable it is a commercial advantage to be ableto produce a coating having easily controlled degrees of density ofshades or tones of color. This control has been difficult to obtainparticularly when employing certain colors, such as blue or green inwhich the pigments themselves have very little covering power or depthof color. In such cases, it 18 possible, according to the presentinvention, by raising the pre-heating temperature, for instance, to therange of 100 to 159 C. and manipulating the spray gun, to build up thecoating Very rapidly, and, in relatively short time, produce a deep richcolor equal to that which was heretofore only attainable by theapplication of several independent relatively thick coatings at the costof an excessive amount of time.

Another advantage derived from the-present method resides in theuniformity of the coating, irrespective of the weather conditions.Heretofore, it has taken a longer time interval to coat a lamp properlyon days when the atmosphere contained a relatively high degree ofmoisture than the time the same operation consumed on dry days. Thiscondition arose from the fact that, onmoist 'days the difference intemperature between the bulbs and the atmosphere results in theaccumulation of a layer of moisture or condensate upon-the bulbs which,when the coating was applied, produced a diluted substance which wouldrun or flow over the surfaces of the bulbs. Therefore, the timenecessary to sufliciently dry out the coating on moist days wasconsiderably increased. This contingency greatly reduced the production,whereas, by pre-heating the lamps, as in the present method, the numberof lamps coated per minute remains constant, irrespective ofmeteorological conditions and, as has been stated, is approximatelytwice that possible by the method used heretofore.

It-has also been found advantageous to heat the air employed forejecting the fluid from the spray gun, or the coating material may beheated prior to its discharge from the spray gun and, when heated, mayeither be applied to a cool surface or to a surface that has beenpre-heated.

In practicing the present method, a lamp to be coated may be pro-heatedto a given temperature in any desired manner. For example, the lamp maybe subjected to a blast of heated air. A coating as, for example, thatset forth in the above mentioned co-pendiiig application, is thenpreferably sprayed upon the surface of a lamp which is passed into aheat zone for a dehydrating treatment after which the setting solutionis applied to the coating, then the bulb is passed through a second heatzone for drying. The bulb may then be washed and subsequently dried bypassage through a heat zone.

Although the above description relates particularly to the treatment ofelectric incandescent lamps, it is to be understood that the method hasother applications as, for instance, it maybeemployed for the treatmentpi objects such as reflectors, globes,.. or the lVhat is claimed 'is:'

1. The method of applying a silicate coating to a light diflusingvitreous object which comprises heating the object and spraying thecoatingthereon while the object is still heated.

2. The method of applying a silicate coating to alight diffusingvitreous object which comprises subjecting the object to a blast ofheated air and projecting the coating in a divided state against theobject.

' 3. The method of coating a vitreous incandescent electric lamp bulbwhich comprises heating said bulb, spraying a silicate coating thereonand in subsequently heating the coated object to dehydrate the coating.

4.' The method of applying. a silicate coating to an incandescentelectric lamp bulb which comprises subjecting the bulb to a blast ofheated air to bring it to a predetermined, temperature, spraying acoating upon the heated bulb and passing the coated bulb through a heatzone.

j 5. The method of applying a silicate coating'to anincandescent'electric lamp bulb which comprises heating the coatingmaterial spraying said heated coating upon said bulb and in passing thecoated bulb through a heat zone.

6. The method of coating an incandescent electric lamp bulb with asilicate coating which comprises heating air under pressure and drivingthe coatingmaterial against the object by said air.

mane

in driving said heated coating in a finelydivided state against the bulband in passing said coated bul through a heat zone.

9. The method of coating an incandescent electric lamp bulb with asilicate coating which consists in heating the bulb and applying thecoating thereto by spraying while the bulb is still warm to deposit aplurality ing a so vof layers of'said coating upon the bulb.

10. The method of applying a silicate coating ;of a given densit to anincandescent electric lamp bulb which com rises heating the bulb to apredetermined temperature and in spraying the coating material upon saidbulb while the same is still warm to de-' posit a plurality of layers ofsaid material upon the bulb.

11. The process of afiixing a coating to a silicious article comprisingheating the article, spra ing thereon a preparation containub esilicate, subjecting the article to heat and applying a heated solutionof at least one substance which reacts with the sodium silicate to forman insoluble com pound. 4

12. The process of aflixin a. coat1ng to silicious articles comprisingeating the articles applying thereto a preparation containing a solublesilicate, akmg said applied preparation, applying a hot solut on ca ableof reacting with the sihcate, rinsing said articlesand subsequentlydrying the 7 same.

13. The process of afiixing a coating to silicious articles comprisingheating the articles, applying thereto a preparation havmg sodiumsilicate as one of its ingredients,

baking saidpreparation, treating said baked preparation with a settingsolution and heatmg to cause a reaction with the sodium silicate.

14. The process of afiixing a coating to silicious articles comprisingheating the arzticles, applying thereto a reparation includng a fillerand sodium silicate, baking said preparation and applying a's'econdpreparation to react with the sodium silicate for the formation of aninsoluble compound. I

In testimony whereof, I have hereunto subscribed my name this 6th day ofJuly ALBERT FERDINAND LINDS'I'ROI.

